Hi everybody.

there is a Compaq 6735s (6050A2235601-MB-A03) motherboard that with adapter connected there isn't any voltage on the mobo.
inspected the schematics and found that the main mosfet is Q1031 which let's the current flow through circuit, but it's not on, so there isn't any voltage available, although there is 19.5v at source and 19v at gate (you can see in the picture attached). but when i touch the gate pin of Q1031 with my finger (naturally there is a voltage drop at gate), mosfet turns on and current passes through. I then desoldered Q1031 and shorted source to drain on the mobo and notebook started operating without problems. I checked the nearby components although not all of them but the ones I checked are OK.

I don't know why this mosfet doesn't turn on. maybe 0.5v voltage difference on S-G is not enough. Any help will be appreciated.
thanks in advance.

Chek these signals:
ADP_EN# must be 0V.
BUTCAL# must be 0V.

Thanks for the reply.

ADP_EN# is 19v
BATCAL# is 18.3v

in order to operate normally, should they be zero?

I think so.
Update BIOS, and try to chek CHGCTRL_3. May by KBC1091 (118 pin) do not generate this one.

Will try the BIOS, but I think it's not BIOS related, because in current state there isn't any voltage available on board and all BIOS IC pins are 0v, so BIOS is not readable at all in current situation, but when I short Q1031 source to drain, voltage becomes available and I can turn on the laptop normally.

Also checked KBC pin 118, there is nothing there, 0v.

Thanks and I really appreciate the time and effort.

You have no +VBAT. Chek ADP_PWRID and LIMITsignal. Maybe U1024-A is out of order.

Thanks and sorry for the late reply, I wasn't able to post for a couple of days. I will check.